This invention relates to a pollenizer watermelon plant, for use in the production of seedless watermelon.
The pollenizer plant is characterized by at least two of the following features: (a) distinguishable fruit phenotype; (b) high number of male flowers; (c) continued flowering; (d) early flowering; and/or (e) modified plant morphology and growth habit.
The invention particularly relates to plants having the characteristics of plants grown from the seed deposited at the ATCC under ATCC accession number 203961. The invention further relates to plants obtainable by propagation of, and/or breeding with a watermelon plant grown from the seed deposited at the ATCC under ATCC accession number 203961.
All documents cited herein are hereby incorporated herein by reference.
Fruit of standard seeded watermelon varieties may contain as many as 1,000 seeds in each fruit. Hybrid seedless (triploid) watermelons have been grown for over 40 years in the United States. However, it was not until recently that improved varieties, aggressive marketing, and increased consumer demand created a rapidly expanding market for seedless watermelons.
The seedless condition in watermelon actually results from a cross between two plants of incompatible chromosome complements. The normal chromosome number in most living organisms is referred to as xe2x80x9c2Nxe2x80x9d. Seedless watermelons are produced on sterile triploid (xe2x80x9c3Nxe2x80x9d) plants, which result from crossing a normal seeded diploid (2N) plant with a tetraploid (xe2x80x9c4Nxe2x80x9d). Tetraploid parental lines are usually developed by treating diploid plants with colchicine, which induces a doubling of the chromosome number.
To produce a harvest of seedless watermelons, the triploid plants must be interplanted with a pollenizer variety (xe2x80x9c2Nxe2x80x9d). As the pollen from the triploid plants is sterile and unable to stimulate fruit set, pollen from fertile diploid plants must be provided. In the U.S., growers generally use Allsweet type hybrids as a pollen source as these provide themselves marketable fruit. The commercial seedless (triploid) plants and the pollenizer variety are normally seeded in separate flats and transplanted after about 4 weeks to the field. Close interplanting between triploid plants and pollenizers is required to enable bees to transfer sufficient pollen to the triploid plants, as inadequate pollination results in seedless fruit that are triangular in shape and of poor quality. Most growers place the pollenizer plants in every third row (to aid in harvesting) or every third plant in the row. This will lead to a field wherein two thirds of the fruit is seedless and one-third of the fruit is seeded. Usually, the pollenizer variety is selected to produce fruit that is distinguishable from the seedless variety, to avoid mixing of the seeded and seedless fruit after harvest.
Inter-planting of plants producing seeded with plants producing seedless fruit in the same field has significant agronomical drawbacks. First, the two different types of plants grow at different rates and the timing of water and fertilizer application for the two varieties often is not synchronized. Maturity dates also vary so that multiple harvests must be used. More importantly, the difference in development can cause problems as it is crucial that pollen from the diploid pollenizer is available when the female blossoms on the triploid plant are open and ready for pollination. This is complicated by the fact that diploid plants producing seeded fruit stop flowering once they have set fruit, so that pollen is no longer available for seedless fruit development.
The invention relates to a pollenizer watermelon plant, for use in the pollination of triploid watermelon plants in the production of seedless watermelon. The pollenizer plant of the invention is characterized by at least two, preferably three, more preferably four, most preferably five of the following features:
a) distinguishable fruit phenotype;
b) high number of male flowers;
c) continued flowering;
d) early flowering; and/or
e) modified plant morphology and growth habit.
The invention particularly relates to a pollenizer plant characterized by at least two, preferably three, more preferably four, most preferably five of the following features: fruit produced on the plant weighs less than 5 lbs. each and/or is less than 15 cm in diameter; at least 20 male flowers are grown per plant per day during triploid flowering period; fruit set does not halt flowering, male flowers open at least 10 minutes earlier than commercial triploid plants; a diameter of the vine that is 65% or less of the diameter of a commercial diploid plant and/or a prostrate growth habit.
These features may be present in the pollenizer plant of the invention, in any and all possible combinations; any two, three, four or five of the features may be present in any possible combination. For example, the plant may have a distinguishable fruit phenotype together with a high number of male flowers, and/or continued flowering, and/or early flowering, and/or modified plant morphology and growth habit; all other combinations of two, three, four or five of the features are possible and are meant to be included in the invention.
The invention preferably relates to a pollenizer plant characterized by a distinguishable fruit phenotype, a high number of male flowers and continued flowering.
The invention particularly relates to the seed deposited at ATCC under ATCC accession number 203961, a plant which is grown from this seed, and cells or tissues from a plant grown from this seed. The invention further relates to plants obtainable by propagation of, and/or breeding with a watermelon plant grown from the seed deposited at the ATCC under ATCC accession number 203961.
The invention further relates to plant parts and seeds of such pollenizer plants described above.
The invention furthermore relates to a method for producing seedless watermelon, which comprises interplanting seeds or plants of a triploid watermelon line with seeds or plants of the pollenizer line of the invention, and allowing the pollen of these pollenizer plants to pollinate the triploid watermelon plants, so as to stimulate fruitset thereon.
Preferably, seeds or plants of a triploid watermelon line are interplanted with seeds or plants of the pollenizer line of the invention, in specific patterns in the field, whereby these pollenizer plants grow in close proximity to the triploid watermelon plants.
The invention furthermore relates to a method for producing seedless watermelon, whereby seeds of a triploid watermelon line are blended with seeds of the pollenizer fine of the invention prior to sowing.
The invention further relates to a system for producing seedless watermelon which comprises:
seeds capable of growing into triploid watermelon plants, or the plants grown therefrom, and,
seeds capable of growing into the pollenizer plants characterized as described above, or the plants grown therefrom.
Seedless fruit as used herein refers to fruit containing few (less than 5% of seeded fruit which contains at least 500 seeds) or no normal seeds. It is possible that the fruit from the first fruit settings of a seedless plant will contain some (up to 20/fruit) seeds. Also, some varieties designated as xe2x80x9cseedlessxe2x80x9d may contain rudimentary, edible seeds or seed coats. Plants that carry seedless or seeded fruit will also be referred to as seedless or seeded plants, respectively.
As used herein diploid (xe2x80x9c2Nxe2x80x9d), triploid (xe2x80x9c3Nxe2x80x9d) and tetraploid (xe2x80x9c4Nxe2x80x9d) refers to the number of chromosomes in all or in at least the majority of cells in the plant. For the cultivation of seedless watermelon referred to herein, triploid plants are used as female parent plants (for fruit set), while diploid plants are used as the male parent plants (providing pollen).
As used herein, the term xe2x80x9ccomprisingxe2x80x9d means xe2x80x9cincludingxe2x80x9d.
The term xe2x80x9cpollenizerxe2x80x9d or xe2x80x9cpollenizer plantxe2x80x9d refers to a plant that is used to provide pollen for fruit set on suitable female parent plants, preferably triploid plants, and is also referred to as the male parent plant. This does not exclude that the pollenizer can also self-pollinate and set fruit. A number of measures are taken to ensure that pollen from the pollenizer plant can indeed pollinate the plant on which fruit set is to occur, such as, but not limited to, adequate interplanting and providing an adequate bee population.
A commercial diploid pollenizer line (or plant of such a line) as used herein refers to inbred or hybrid lines which are commercially used at the time of the present invention as pollenizers in the production of seedless watermelon. These lines are generally selected based on the marketability of the (seeded) fruit produced on the plants. For the purposes of this invention, representative examples of commercial diploid pollenizer lines are Calsweet, Sangria and Royal Sweet. These commercial diploid lines are all comparable with regard to fruit phenotype, number of male flowers, start and duration of flowering and plant morphology and growth habit.
The terms commercial triploid watermelon plants and commercial seedless watermelon as used herein refer to the seedless plants and fruits marketed. These seedless plants yield seedless fruit as defined herein. Usually, the seedless fruit has a diameter of at least 15 cm and/or a weight of at least 10 lbs. when harvested.
The pollenizer plants of the present invention display certain characteristics, which provide specific advantages for their use as pollenizer plants in the production of seedless watermelon. The characterizing features, which are evaluated, are as follows:
a) Distinguishable Fruit Phenotype
Distinguishable fruit phenotype refers to the fact that the phenotype of the fruit differs from that of the commercial seedless watermelon produced by commercial seedless triploid plants, in a way that can easily be established. Preferably, this phenotype is measurable in weight and/or size. More preferably, the fruit produced by the pollenizer plants of the present invention weighs less then ten, most preferably less than five lbs., especially preferably less than four lbs. each. Additionally or alternatively, the diameter of the fruit produced on the pollenizer plant of the invention is less than 15 cm, preferably less than 12 cm, more preferably less than 10 cm, most preferably less than 8 cm in diameter on average. The difference in fruit phenotype between that the seedless fruit and that of the pollenizer plant of the invention can optionally be increased by a difference in color or rind pattern. As commercial seedless watermelon is in many cases striped, the pollenizer plant of the invention preferably produces fruit with a distinguishable rind pattern. Alternatively, the difference in phenotype can be a difference in shape.
b) High Number of Male flowers
The number of male (staminate) flowers refers to the number of male flowers present on a pollenizer plant per day, during the blooming period of the female blossoms of the triploid plant, hereinafter also referred to as xe2x80x9ctriploid blooming periodxe2x80x9d (plants of diploid watermelon lines will generally start producing flowers 7 to 10 days before the female blossoms of triploid watermelon lines start to open, but these days are not taken into account as no pollination of triploid flowers can occur during this time). The number of male flowers on the pollenizer plant of the invention is preferably at least 20, more preferably 30, especially preferably 40, most preferably 50 flowers per plant per day during the triploid blooming period. Alternatively, the number of flowers can be expressed as compared to commercial diploid lines and will preferably be at least twice, more preferably three times, especially preferably four times, most preferably five times (or more) the number of male flowers produced on a commercial diploid line.
c) Continued Flowering
In commercial diploid watermelon lines the start of fruit set on some of the flowers will stop the flowering on the rest of the plant. The pollenizer plants of the invention are preferably characterized in that they will continue to produce male flowers, even after fruit set has started.
d) Early Flowering
Male flowers on commercial diploid lines open at the same time or slightly later than the female triploid blossoms. The characteristic of early flowering (or anthesis) of the pollenizer plant of the invention can thus be determined relative to that of either commercial diploid pollenizer plants or commercial triploid watermelon plants. Preferably the flowers of the pollenizer of the invention will start to open at least 10 minutes, more preferably at least 15 minutes, especially preferably at least 20 minutes, most preferably 30 minutes or more before the female blossoms of the triploid watermelon (or a commercial diploid pollenizer) open and are receptive to pollen.
e) Modified Plant Morphology and Growth Habit
The morphology and growth of the pollenizer plants of the invention is preferably characterized by one or more of a number of features which differ from those of commercial diploid pollenizer lines. Standard commercial diploid pollenizer plants display a plant morphology and growth which is similar to that of a triploid plant, or are only slightly more slender in stem diameter. The pollenizer plants of the invention preferably have remarkably more slender vines and runners, more preferably the diameter of the vines will be less than 75%, most preferably less than 65%, especially preferably 50% or less than the diameter of the vines of a triploid watermelon plant in the same stage of development. Additionally or alternatively, the pollenizer plant will preferably display an overall prostrate growth. Additionally, the flowers of the pollenizer plant of the invention can display an altered morphology, such as a color difference, which makes them more attractive to visiting insects.
Interplanting refers to the combination of two or more types of seeds or plants sown or transplanted on a field. As watermelon fruit set and enlargement is dependent upon growth regulators from the pollen grains and from embryos in developing seeds within the fruits, adequate pollination is important for quality and quantity of the fruit. Interplanting can occur at random, by mixing seeds before sowing, or can be the result of a specific field arrangement of seeds or transplanted plantlets.
Maynard xe2x80x9cGrowing Seedless Watermelonsxe2x80x9d, HS 687, March 1996, relates to examples of field arrangements which have been used successfully for the production seedless watermelon using standard current practice. The field arrangements can be obtained by direct sowing of seeds in the field or by transplanting seeds grown in separate flats.
Interplanting of commercial diploid and triploid lines is usually done at a ratio of 1:2, to ensure adequate pollination of the triploid flowers. The pollenizer plant of the present invention can also be interplanted with a commercial triploid line at a 1:2 ratio. However, since the pollenizer of the invention has more male blossoms and is more slender and less competitive, adequate pollination of the triploid plants can be obtained when interplanting occurs at a lower ratio (1:3 to 1:5, or less).
Cross-pollination as used herein refers to the pollination of the flowers of the female (preferably triploid) parent plants with pollen from the flowers of a pollenizer plant which leads to the production of seedless fruit.
An object of the present invention is to increase the number of seedless fruit produced per acre in a field. The use of the pollenizer of the invention allows a higher triploid population per acre and increased pollination efficiency resulting in higher yield of seedless fruit and thus increased income for the grower.
According to the present invention, pollenizer plants are obtained which can be used in, and provide important advantages for, the production of seedless watermelon. The plants of the invention are characterized by at least two, preferably three, more preferably four, most preferably five of the characteristics selected from the group consisting of: distinguishable fruit phenotype, high number of male flowers, continued flowering, early flowering, and modified plant morphology and growth habit.
These characteristics directly or indirectly provide advantages for the use of the pollenizer plant of this invention in the production of seedless watermelon. The production of easily distinguishable fruit by the pollenizer line facilitates the harvesting of fruit. The pollenizer plant of this invention may produce fruit which is small and in fact unmarketable, eliminating all need for a separate harvest or separation of the seedless and seeded fruit after harvest.
As the pollenizer plant of this invention preferably produces large numbers of male blossoms, it can provide more pollen for fruit set on female parent plants. Both by the number of flowers and/or their morphology (including flower color), this plant is preferably more attractive to bees than the commercial diploid pollenizers, which also stimulates pollination. Preferably, the start of fruit set does not affect flowering on the pollenizer plant of this invention, which means that it is capable of providing pollen over a longer period of time. Furthermore, flowering will preferably occur earlier on the pollenizer plant of the invention than on the female parent (triploid ) plants, which is advantageous for cross-pollination of the female parent plants, as this ensures that bees will be carrying pollen from the pollenizer line by the time the flowers on the female parent plant open. The runners on the pollenizer plant of this invention are preferably long and slender which places its male flowers in closer proximity to the flowers on the seedless plants. Also, the pollenizer plant of this invention is preferably more slender, allowing it to be more invasive while less competitive to the female (triploid) parent plants. This makes it possible to more closely interplant the pollenizer of the invention with the triploid line, allowing better cross-pollination conditions, without negatively affecting development or fruit set of the seedless plants.
The use of the pollenizer of the present invention in the production of seedless watermelon thus can provide the following important advantages, as compared to commercial diploid pollenizers, for the grower:
1) The possibility to increase the number of triploid plants (or other female plants) per acre will result in an increased number of seedless fruit harvested per acre, resulting in higher income to the grower because these sell for a premium price.
2) A longer production period due to the fact that the pollenizer plants of this invention continue to produce male blossoms and pollen much longer than commercial diploids, also positively influencing seedless fruit yield.
3) Improved fruit set because the flowers on the pollenizer plants are more attractive to bees, the long runners on these plants intermingle better with the seedless plants, and the plants produce more male blossoms than standard diploid pollenizers. This again will positively affect yield of seedless fruit.
4) Growers can grow fields from which exclusively seedless fruit is harvested. This eliminates problems of mixing with seeded fruit.
Secondary, but also significant advantages can be:
5) Harvesting costs are reduced since the grower no longer has to harvest when the seeded fruit are ready and again when the seedless fruit are ready.
6) Production practices can be optimized since the grower is not having to compromise some practices because of different growth rates for seeded and seedless plants.
A preferred embodiment of the invention is a pollenizer plant characterized by the following features: a) distinguishable fruit phenotype, b) high number of male flowers, c) continued flowering, d) early flowering and e) modified plant morphology and growth habit.
An especially preferred embodiment of the invention is a pollenizer plant characterized by the fact that the fruit produced on the plant weighs less than 5 lbs. each and/or is less than 15 cm in diameter, that it produces at least 20 male flowers per plant per day during triploid flowering period, that fruit set does not halt flowering, that its male flowers open at least 10 minutes earlier than commercial triploid plants, and that the diameter of its vines is 65% or less the diameter of a commercial diploid plant.
Plants according to the preferred embodiment of the invention can be obtained form the seeds deposited at the ATCC under ATCC accession number 203961. Such plants can further be propagated to produce more plants with the same characteristics.